Laminated magnetic core for induction devices and laminations for forming such magnetic core

ABSTRACT

A laminated magnetic core for electric induction devices comprising a shell formed of laminations. Each of said laminations comprising two parallel yoke legs and two outer legs arranged between and perpendicular to such parallel yoke legs. A central leg is disposed parallel to the outer legs and forms with one of said parallel yoke legs an air gap. Each of the laminations of the shell embodying similar U-shaped lamination elements comprising a respective outer leg and unequal length yoke leg sections protruding from the ends of such respective outer legs. These lamination elements bear against one another at the end faces of their longer yoke leg sections to form a shell lamination for the magnetic core. Further, such lamination elements bear at the end faces of their shorter yoke leg sections against a central web forming the central leg and arranged between such shorter yoke leg sections.

United States Patent Meili 154] LAMINATED MAGNETIC CORE FOR INDUCTIONDEVICES AND LAMINATIONS FOR FORMING SUCH MAGNETIC CORE [72] Inventor:Ernst Meili, Zurich, Switzerland [73] Assignee: Elektro-Apparatebau F.Knobel &

- Co., Ennenda, Switzerland 22 Filed: Dec.27, 1971 21 Appl. No.: 212,454

[30] Foreign Application Priority Data [58] Field of Search ..336/l30,134, 178, 212, 214, 336/215, 234, 132

[56] References Cited UNITED STATES PATENTS Baenziger et al. ..336/234 X1451 Sept. 26, 1972 FORElGN PATENTS OR APPLICATIONS 803,914 11/1958Great Britain ..336/1 78 Primary Examiner-Thomas J. Kozma Attorney-Ericl-l. Waters et al.

[5 7] ABSTRACT A laminated magnetic core for electric induction devicescomprising a shell formed of laminations. Each of said laminationscomprising two parallel yoke legs and two outer legs arranged betweenand perpendicular to such parallel yoke legs. A central leg is disposedparallel to the outer legs and forms with one of said parallel yoke legsan air gap. Each of the laminations of the shell embodying similarU-shaped lamination elements comprising a respective outer leg andunequal length yoke leg sections protruding from the ends of suchrespective outer legs. These lamination elements bear against oneanother at the end faces of their longer yoke leg sections to form ashell lamination for the magnetic core. Further, such laminationelements bear at the end faces of their shorter yoke leg sectionsagainst a central web forming the central leg and arranged between suchshorter yoke leg sections.

8 Claims, 6 Drawing Figures BACKGROUND OF THE INVENTION The presentinvention broadly relates to improvements in laminated magnetic coresfor electric induction devices and also pertains to new and improvedpunched magnetic core laminations for such cores, such magnetic corecomprising a shell formed of two yoke legs which are parallel to oneanother, two outer legs disposed between and extending perpendicular tosuch parallel yoke legs and a central leg which is parallelto the outerlegs, which central leg together with one of the yoke legs forms an airgap. I

Laminated shell cores for electric induction devices are known to theart which possess an E-shaped component with equal length legs which areinterconnected with one another through the agency of an I-shapedportion serving as a yoke. The individual laminations of such laminatedmagnetic core are stamped-out of a sheet metal member without waste bymeans of the socalled DIN-cut, wherein in each case two E-shapedportions having their legs abutting one another at their ends aresimultaneously stamped-out and from the windows formed by the abuttinglegs there arestamped-out two I-shaped portions.

However, if it is desired to form for such shell core an air gap betweenthe central leg of the E-shaped portions and the I-shaped portion, then,the I-shaped portion must be appropriately spaced from the E-shapedportion, so that air gaps appear also between the outer legs and thel-shaped portion, something which is undesired because of the occurringstray or leakage flux.

Now, in British Pat. 671,823 there is described a laminated magneticcore which is constructed similar to the previously described shellcore, and wherein the last-mentioned drawbacks are overcome in, that anessentially I-shaped yoke leg constructed widened at its ..ends bearsagainst the outer legs of the equal length legs of the E-shaped portion,whereas between the central leg and the central portion of the yoke legwhich is narrow in contrast to the ends there is formed an air However,this air gap cannot be changed in size, since when the magnetic core isassembled together the spacing between the central leg and the yoke legcannot be altered.

Additionally, if the individual laminations are stamped-out withoutwaste similar to the previously described DIN-cut, then, apart from thel-shaped portion also the legs of the E-shaped portion possess unequalwidth.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of thepresent invention to provide a new and improved construction oflaminated magnetic core for induction devices which overcomes thepreviously mentioned drawbacks, the inventive magnetic core being formedof novel punched laminations.

Another objective of this invention is to provide a laminated magneticcore, the air gap between the central or middle leg and one yoke leg ofwhich can be varied and the laminations of which additionally can bestamped-out from sheet metal without waste.

Now in order to implement these and still further objects of theinvention, which will become more readily apparent as the descriptionproceeds, the laminated magnet core of the present invention ismanifested by the features that shell possesses similar U-shaped shellor lamination elements formed from a respective outer leg and unequallength yoke leg sections or portions shorter yoke leg sections andembodying the central leg.

us. Pat. No. 3,201,731 teaches to the art forming the laminations fromU-shaped shell portions with different length legs by punching such outfrom a strip of constant width, wherein, in each case, two laminationswhich mutually interengage with one another with their shorter legsbetween the legs of the other lamination so as to form a gaplessrectangle are conjointly punchedout. With a shell core as illustrated inthe previously mentioned United States Patent and formed of such typepunched-out laminations and in contrast to the inventive magnet core, itis necessary that four such laminations be assembled together in orderto form a shell core cross-section. Additionally, such shell core doesnot possess at its central leg any adjustable air gap.

BRIEF DESCRIPTION OF THE DRAWING The invention will be better understoodand objects other than those set forth above, will become apparent whenconsideration is given to the following detailed description thereof.Such description makes reference to the annexed drawing wherein:

FIG. 1 is a plan view of a first embodiment of magnetic core forelectric induction devices formed of sheet metal laminations constructedaccording to the teachings of the present invention;

FIG. la and 1b illustrate the punching cuts used for fabricating thesheet metal laminations for the magnetic core of FIG. 1;

FIG. 2 is a plan view of a second embodiment of magnet core for anelectric induction device formed of sheet metal laminations; and

FIGS. 2a and 2b illustrate the punching cuts used for fabricating thesheet metal laminations for producing the magnetic core of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Describing now thedrawings, each of the laminated magnet cores 50 (FIG. 1) and 60 (FIG. 2)as illustrated in the drawings will be seen to respectively embody acentral or middle leg 13 and 23 and a respective shell 51 and 61surrounding such legs consisting of two outer legs 11a, 12a and 21a, 22arespectively and two yoke legs 11b, 12b and 110, 12c and 21b, 22b and21c, 220 respectively and forming the magnetic short-circuit path. Thecross-section of the relevant central leg is essentially twice as largeas that of the shell, since the total magnetic flux in the central legis subdivided in such a manner that only one half of the flux flowsthrough the shell. Consequently, with constant thickness of the magneticcore the central leg can be twice as wide as the jacket.

-ment 11 and 12 comprises a respective outer leg 11a and 12a and twoyoke leg portions or sections 11b, 11c and 12b, 120 respectively,extending perpendicular to the associated outer leg 11a and 12arespectively and protruding from the ends of such outer legs, as shown.Both of the lamination elements 11 and 12 abut against one another atthe free ends of their longer yoke leg sections 11b and 12b. In theintermediate space formed by both shorter yoke leg sections 11c and 120there is accommodated a central web 13 which is disposed parallel to theouter legs 11a and 12a, this central web 13 embodying the central legand simultaneously filling-out the intermediate compartment or spaceformed at the lamination and which is located between the shorter yokeleg sections 1 1c and 120. A respective window opening 14 is formedbetween the central web or leg 13 and each of the outer legs 11a and12a, as shown.

The central web or leg 13 together with the yoke leg formed from thelonger yoke leg sections 11b and 12b forms an air gap 16. For thepurpose of adjusting the size of this air gap 16 the central web 13 canbe displaceably 'guidedin its lengthwise direction by means of theshorter yoke leg sections 1 1c and 120.

The dimensions of the laminated magnet core 50 are chosen in such amanner that the laminations thereof can be fabricated by means of apunching or stampingcut to be described more fully in conjunction withthe showing thereof depicted in FIGS. la and 1b. With a lamination widthof dimension a and a central web width of 2a, there is obtained a magnetcore having the outside dimensions 40 to 6a and with window openingopenings 14, the height of which amounts to 24 and the width of whichamounts to a. The length of the shorter yoke leg sections 116 and 120amounts to 2a and is smaller by the amount a than the length of thelonger yoke leg sections 1 lb and 12b.

FIGS. 1a and lbillustrate the manner in which the lamellae of thelamination or shell elements 11 and 12 with their unequal length yokeleg sections 11b and 120 and 11c and 12b bearing against one another,together with a lamellae of the central web 13, can be assembledtogether into a gapless rectangle with the side lengths possessing thedimensions 4a and a. The individual rectangles can be lined up adjacentone another into a strip of constant width, possessing the dimension 5ain FIG. la and the dimension 4a in FIG. lb. The individual sheet metallaminations of the laminated magnetic core importantly can bepunched-out of such sheet metal strips 15 without waste when there isprovided the rectangular arrangements depicted in FIGS. la and 1b.

The laminations forming the shell 61 of the magnet core 60 illustratedin FIG. 2, similar to the magnetic core illustrated in FIG. 1, eachconsist of two similar U- shaped lamination or shell elements 21 and 22,each of which possesses a respective outer leg 21a and 22a equipped witha respective yoke leg section 21b, 21c and 22b, 220 which protrude fromand extend perpendicular to the associated outer legs 21a and 22a. Thelamination elements 21 and 22 which abut one another by means of thefree ends of both of their longer yoke leg sections or portions 21b and22b form a lamination 61 which possesses an intermediate space betweenthe shorter yoke leg sections 210 and 22b, as shown. This intermediatespace is filled by a central or middle web 23 which is disposed parallelto the outer legs 21a and 22a and embodies the central leg. This centralweb 23, similar to the central web 13 of FIG. 1, can be displaced in itslengthwise direction, so that there is obtained an adjustment of the airgap 26 at the central or middle leg. Between the central leg 23 andouter legs 21a and 22a there are formed window openings 24.

With a lamination width of dimension a and a central web width of 2athis magnet core possesses a height of the window openings 24 of a. Thewidth b of this window opening 24, on the otherhand, can be freelyselected. The shorter yoke leg sections 210 and 220 are shorter by theamount a than the longer yoke leg sections 21b and 22b respectively. Itis thus possible to form magnetic cores which possess outside dimensionsof 3a and 4a 2b.

In FIGS. 2a and 2b there is illustrated the manner in which tworespective lamellae of the lamination 'elements 21 and 22 can beinterleaved or interfitted in pairs with one another. The respectiveshorter yoke leg sections 210 or 220 of the one lamination element 21 or22 always engages between the yoke leg sections 220, 22b or 21b, 210 ofthe other jacket element and fills the space forming the window openings24. Each two lamellae of the lamination elements 21 and 22 form agapless rectangle with the sides having the dimensions 4a and 2a b.

The lamellae of the lamination or shell elements 21 and 22 can bepunched-out in the form of such abutting rectangles from a strip 25 ofconstant width, possessing the dimension 2a b (FIG. 2a) and thedimension 4a (FIG. 2b). The central webs or legs 23, which possesses asquare cross-section with a side length dimension of 2a, are likewisepunched-out free of waste from a second sheet metal strip (notillustrated) having a width possessing the dimension 2a.

With the laminated magnet core of the type illustrated in FIGS. 1 and 2the respective air gap 16 or 26 at the relevant central web or leg 13 or23 can be easily adjusted without having to tolerate any undesired airgap at the lamination 51 or 61 respectively.

The described magnetic cores 50 and are preferably used for inductanceor choke coils for the operation of fluorescent tubes. In so doing, itis important to dimension the magnet core in such a fashion that withouteconomical or technological drawbacks there is obtained a lowconstructional height of the series connected devices. Above all it hasbeen found that the magnetic core of FIG. 1, owing to itscross-sectional dimensions of 4a and 6a is particularly suitable forseries connected devices. The height of this magnetic core in relationto its width is in a ratio of 1:1.5, rendering possible the economicalconstruction of series connected devices of low structural height,whereby material can be saved at the socket of the fluorescent tubes,also bringing with it advantages as concerns lighting technology andaesthetic effect.

If with the embodiment of FIG. 1 there is selected for the dimension athe value of 6.4 cm., then, there is obtained a magnetic core with theparticularly favorable cross-sectional dimensions of 38.4 X 25.6 cm.

If the magnetic cores are arranged in a housing formed of sheet iron,then, in certain cases it is desired to incorporate such iron sheetmetal housing as active component in the magnetic circuit. In this casethe lamination elements are reduced in their width by an amountcorresponding to the thickness of the sheet iron used for the housing,so that the width thereof is a little smaller than half the width of thecentral web.

While there is shown and described present preferred embodiments of theinvention, it is to be distinctly understood that the invention is notlimited thereto but may be otherwise variously embodied and practicedwithin the scope of the following claims. Accordingly,

What is claimed is:

l. A laminated magnetic core for induction devices comprising a shellformed of laminations and possessing two yoke legs parallel to oneanother and two outer legs arranged between and perpendicular to saidparallel yoke legs, a central leg disposed parallel to said outer legsand forming with one of said parallel yoke legs an air gap, each of saidlaminations embodying similar substantially U-shaped lamination elementscomprising a respective outer leg and unequal length yoke leg sectionsprotruding from the ends of said respective outer legs, said laminationelements bearing against one another at the end faces of their longeryoke leg sections to define one of said parallel yoke legs with theremaining shorter yoke leg sections defining the'other parallel yokeleg, and a central web embodying said central leg arranged between saidshorter yoke leg sections, said lamination elements bearing at the endfaces of their shorter yoke leg sections against said central webdisposed between said shorter yoke leg sections.

2. The laminated magnetic core as defined in claim 1, wherein said yokeleg sections and said outer legs possess essentially the same width andin relation to said central web practically half the width thereof, andwherein the length of each outer leg corresponds to the width of saidcentral web, each longer yoke leg section being three times as long aswide, and each longer yoke leg section being longer by an amountcorresponding to its width than the length of each shorter yoke legsection, the length of said central web essentially corresponding tothree times the width of said outer leg, so that two of said laminationelements with the end faces of their yoke leg sections bearing againstone another together with said central web surrounded by said twolamination elements can be assembled together into a gapless rectangle.

3. The laminated magnetic core as defined in claim 1, wherein said yokeleg sections and each said outer leg essentially possess the same widthand with respect to said central web practically one-half of the widththereof, said central web essentially being as long as it is wide, thelength of each outer leg corresponding to its width, each said longeryoke leg section being longer than each said shorter yoke leg sectionsby an amount corresponding to its width, so that two lamination elementsmutually engage with their shorter yoke leg sections between the yokeleg sections of the other lamination element so as to be assembledtogether into a gapless rectangle.

4. The laminated magnetic core as defined in. claim l, wherein saidcentral w eb arranged betwee both of eg sections is guided to beisplaceasaid shorter yoke ble in its lengthwise direction by saidshorter yoke leg sections.

5. A lamination'for the magnetic core of electric induction devicescomprising similar substantially U- shaped lamination elements eachpossessing a respective outer leg and unequal length yoke leg sectionsprotruding from the ends of its associated respective outer leg, saidlamination elements bearing against one another at the end faces oftheir longer yoke leg sections to define one parallel yoke leg with theremaining shorter yoke leg sections defining another parallel yoke leg,and a central web arranged between said shorter yoke leg sections, saidlamination elements hearing at the end faces of their shorter yoke legsections against said central web.

6. The laminated magnetic core as defined in claim 5, wherein said yokeleg sections and said outer legs possess essentially the same width andin relation to said central web practically half the width thereof, andwherein the length of each outer leg corresponds to the width of saidcentral web, each longer yoke leg section being three times as long aswide, and each longer yoke leg section being longer by an amountcorresponding to its width than the length of each shorter yoke legsection, the length of said central web essentially corresponding tothree times the width of said outer leg, so that two of said laminationelements with the end faces of their yoke leg sections bearing againstone another together with said central web surrounded by said twolamination elements can be assembled together into a gapless rectangle.

7. The laminated magnetic core as defined in claim 5, wherein said yokeleg sections and each said outer leg essentially possess the same widthand with respect to said central web practically one-half of the widththereof, said central web essentially being as long as it is wide, thelength of each outer leg corresponding to its width, each said longeryoke leg section being longer than each said shorter yoke leg sectionsby an amount corresponding to its width, so that two lamination elementsmutually engage with their shorter yoke leg sections between the yokeleg sections of the other lamination element so as to be assembledtogether into a gapless rectangle.

8. The laminated magnetic core as defined in claim 5, wherein saidcentral web arranged between both of said shorter yoke leg sections isguided to be displaceable in its lengthwise direction by said shorteryoke leg sections so as to form an adjustable size air gap.

1. A laminated magnetic core for induction devices comprising a shellformed of laminations and possessing two yoke legs parallel to oneanother and two outer legs arranged between and perpendicular to saidparallel yoke legs, a central leg disposed parallel to said outer legsand forming with one of said parallel yoke legs an air gap, each of saidlaminations embodying similar substantially U-shaped lamination elementscomprising a respective outer leg and unequal length yoke leg sectionsprotruding from the ends of said respective outer legs, said laminationelements bearing against one another at the end faces of their longeryoke leg sections to define one of said parallel yoke legs with theremaining shorter yoke leg sections defining the other parallel yokeleg, and a central web embodying said central leg arranged between saidshorter yoke leg sections, said lamination elements bearing at the endfaces of their shorter yoke leg sections against said central webdisposed between said shorter yoke leg sections.
 2. The laminatedmagnetic core as defined in claim 1, wherein said yoke leg sections andsaid outer legs possess essentially the same width and in relation tosaid central web practically half the width thereof, and wherein thelength of each outer leg corresponds to the width of said central web,each longer yoke leg section being three times as long as wide, and eachlonger yoke leg section being longer by an amount corresponding to itswidth than the length of each shorter yoke leg section, the length ofsaid central web essentially corresponding to three times the width ofsaid outer leg, so that two of said lamination elements with the endfaces of their yoke leg sections bearing against one another togetherwith said central web surrounded by said two lamination elements can beassembled together into a gapless rectangle.
 3. The laminated magneticcore as defined in claim 1, wherein said yoke leg sections and each saidouter leg essentially possess the same width and with respect to saidcentral web practically one-half of the width thereof, said central webessentially being as long as it is wide, the length of each outer legcorresponding to its width, each said longer yoke leg section beinglonger than each said shorter yoke leg sections by an amountcorresponding to its width, so that two lamination elements mutuallyengage with their shorter yoke leg sections between the yoke legsections of the other lamination element so as to be assembled togetherinto a gapless rectangle.
 4. The laminated magnetic core as defined inclaim 1, wherein said central web arranged between both of said shorteryoke leg sections is guided to be displaceable in its lengthwisedirection by said shorter yoke leg sections.
 5. A lamination for themagnetic core of electric induction devices comprising similarsubstantially U-shaped lamination elements each possessing a respectiveouter leg and unequal length yoke leg sections protruding from the endsof its associated respective outer leg, said lamination elements bearingagainst one another at the end faces of their longer yoke leg sectionsto define one parallel yoke leg with the remaining shorter yoke legsections defining another parallel yoke leg, and a central web arrangedbetween said shorter yoke leg sections, said lamination elements bearingat the end faces of their shorter yoke leg sections against said centralweb.
 6. The laminated magnetic core as defined in claim 5, wherein saidyoke leg sections and said outer legs possess essentially the same widthand in relation to said central web practically half the width thereof,and wherein the length of each outer leg corresponds to the width ofsaid central web, each longer yoke leg section being three times as longas wide, and each longer yoke leg section being longer by an amountcorresponding to its width than the length of each shorter yoke legsection, the length of said central web essentially corresponding tothree times the width of said outer leg, so that two of said laminationelements with the end faces of their yoke leg sections bearing againstone another together with said central web surrounded by said twolamination elements can be assembled together into a gapless rectangle.7. The laminated magnetic core as defined in claim 5, wherein said yokeleg sections and each said outer leg essentially possess the same widthand with respect to said central web practically one-half of the widththereof, said central web essentially being as long as it is wide, thelength of each outer leg corresponding to its width, each said longeryoke leg section being longer than each said shorter yoke leg sectionsby an amount corresponding to its width, so that two lamination elementsmutually engage with their shorter yoke leg sections between the yokeleg sections of the other lamination element so as to be assembledtogether into a gapless rectangle.
 8. The laminated magnetic core asdefined in claim 5, wherein said central web arranged between both ofsaid shorter yoke leg sections is guided to be displaceable in itslengthwise direction by said shorter yoke leg sections so as to form anadjustable size air gap.